The effects of hippocampal lesions on classical conditioning are compared with the effects of cortical lesions. The cortical lesions are made in the dorsal noradrenergic bundle, which carries all of the locus coeruleus input to the hippocampus. Effects on the lesions are assessed on simple conditioning of the nictitating membrane response, on latent inhibition of the conditioned response, and on extinction of the conditioned response. Brain samples are then assayed for norepinephrine. Subjects are rabbits.